Bearing assembly

ABSTRACT

An arrangement providing positive retention of a bearing on a shaft; the bearing is forced over a specially sized shoulder on the shaft by momentary deformation to a seat and is positively held there.

1.617.085 2/1927 Specht 308/190 Unlted States Patent 1 1 1111 3,797,900Secola 1 Mar. 19, 1974 BEARING ASSEMBLY 2.641.517 6/1953 Meadows 308/1907 7 [75] Inventor: Anthony J. Secola, Hartford, Wis. 913.-84 11/1959Zankl 308/15 [73] Assignee: Chrysler Corporation, Highland FORHGNPATENTS OR APPLICATIONS park, Mich 598.018 2/1948 Great Britain 308/19022 F1 1 16, 1 1 ed Aug 1972 Primary Examiner-Charles J. Myhre [21] App].No.: 281,253 Assistant Examiner-Frank Susko 52 US. Cl. .1. 308/236ABSTRACT [51] Int. C1. F16c 36/06 .[58] Field 61 Search 308/190, 15,236, 189 rrangemem v a bearmg on a shaft; the bear1ngv1s forced over aspe- 56] References Cited ciall y sized shoulder on the shaft bymomentary defor- UNITED STATES PATENTS manon to a seat and 1s posmvelyheld there.

10 Claims, 3 Drawing Figures BEARING ASSEMBLY BACKGROUND This inventionspecifically relates to the assembly of bearing on the crank shaft ofoutboard engines. However, it is applicable to bearing assembliesgenerally wherein a bearing is to be held on a shaft.

In outboard engines the main bearing, which is carried by thecrankshaft, positions the shaft in the engine because the outer race ispositively retained axially in the crankcase housing bore. It is commonin the art to force or press fit the bearing on the shaft. Thecrankshaft is often subjected to forces which tend to displace itrelative to the bearing. Also, the tension resulting from press fittingcauses metal fatigue in the bearing. Because of the reliance on thepress fit of the bearing inner race on the crankshaft for holding theshaft position in the crankcase and its shortcomings, there is a needfor more positive retention of the bearing to the crankshaft.

Typically, bearings for use in this and similar design situations areselected with relatively high internal clearance and are pressed on thecrankshaft with a maximum allowable press to secure proper runningclearance and adequate fatigue life of the race. Taking full advantageof this does not assure adequate axial holding capacity to preventslippage of the crankshaft in the bearing due to vibrations or excessiveloads, such as those experienced when removing the flywheel from theshaft, this usually being accomplished by a series of hammer blows tothe end of the shaft.

Other bearing assemblies, in which a shaft or journal member is pressfitted into an annular bearing, suffer similar retention problems. Thisis particularly true not only with regard to outboard engines but withcrankshaft mountings in lawnmower engines and other two stroke cycleengines as well as in other bearing-journal combinations such asautomotive wheel bearings. This invention is generally applicable to alldesign situations of the foregoing type.

Conventional means of positive retention such as the use of collars,keys, retaining rings and liquid locking agents are impractical in thisand similar design situations due to bulk, added stress concentration orinadequate holding capacity.

This invention provides a solution to this problem which is simple andinexpensive.

SUMMARY OF THE INVENTION The snap fitting of annular members in recessesof various types is generally old. However, such annular members haveheretofore been made of readily deformable, thin materials such asspring steel or plastic. This invention applies the concept torelatively massive structures which are not ordinarily considered to bedeformable, such as annular bearing races, and is particularlyapplicable to the crankshaft main bearing assembly of outboard enginesand the like.

Such crankshafts will, according to this invention, have shoulder meansor the like forming a recessed seat thereon for receiving the innerportion, such as the inner race, of a ball bearing. The shoulder meansis sized such, relative to the inner portion of the bearing, that thebearing can be forceably expanded when pushed over the shoulder means toreach the seat without exceeding the elastic limit of the bearingmaterial or permanently deforming it. A simple low cost arrangement forthe improved positive retention of a bearing, particularly a ballbearing, on a journal, particularly a crankshaft, by using a speciallysized shoulder on the journal, which momentarily takes full advantage ofthe elasticity of the bearing during assembly is thus provided.

Another advantage of this construction is that the bearing is maintainedsecurely in a fixed position on the shaft with less tension and/orradial stress than is necessary when using a press fit. Fatigue lifebeing directly proportional to the tension to which a piece of metal issubjected, the higher the tension the shorter the fatigue life. Usingthe construction provided herein instead of a press fit allows thebearing bore to be sized relative to the shaft so as to minimize tensionand radial stress once the bearing is seated. The momentary tensionexperienced during assembly even though greater than that experienced inpress fitting does not affect fatigue life.

DESCRIPTION OF THE DRAWINGS FIG. 1-is a plan'view of a partiallyassembled bearing and a crankshaft.

FIG. 2 is a detailed view of the shoulder and seat portion of thecrankshaft.

FIG. 3 is a detailed view of an assembled bearing and crankshaft, alsoshowing an optional tool useful in assembling the bearing andcrankshaft.

DESCRIPTION OF THE PREFERRED EMBODIMENT cally to produce line to linefits or interference fits depending on the bearing class allowance. Theseat is preferably defined by shoulder means, such as an integral pairof spaced shoulders 20 and 22, which are preferably annular and extendcontinuously around the shaft like a collar as shown at 20 in FIGS. 1and 2 and, as best shown in FIG. 2.

The outside diameter of the shoulder means can readily be madesufficiently larger than-the diameter of seat 18 for the purposes ofthis invention. On typical ball bearings, presses up to 0.008 inch ormore in diameter are practical depending on particular sizes. Much lowerpresses are practical however. Typically, the ball bearing used in anoutboard engine will require a shoulder diameter of only about 0.002 to0.004 inches larger than the diameter of seat 18 to accomplish mountingas shown in FIG. 3. Generally speaking the CD. of the shoulder may rangefrom about 0.1 to 0.8 percent, 0.4 percent being preferred, larger thanthe ID. of the bearing bore. I

Mounting is accomplished by simply forcing the bearing over shoulder 20during which time the race momentarily expands due to its elasticity toallow its passage over the shoulder to the seat 18. It has apparentlybeen mistakenly assumed in the art that, because bearings fail at lowcontinuous stress levels, a much higher momentary stress as isexperienced in passing over shoulder to seat 18 is also not possible.Therefore this approach has not been seen heretofore.

For short shoulders, a tool 24 shown in phantom in FIG. 3, can beprovided to help pilot the bearing during assembly. To assure long lifeof the tool its diameter can be made slightly smaller than that of theshoulder. The shoulder does not necessarily have to be uniformly roundabout the crankshaft but can extend out from only one point or areathereof. When effective outside diameter is used herein it is meant toencompass both structures.

The success of this design is enhanced by using a relatively hardjournal shaft and bearing race to avoid galling of the bearing race andthe journal. The bearing races themselves are normally hard enough,exceeding about R 60 in hardness. The crankshaft or journal may besofter, down to about R 35 and up to about R,: 60, depending on thematerial. Specific sizes and material hardness will depend on theparticular elements being assembled.

Having described preferred embodiments of the invention, what is claimedas an exclusive property right is defined as-follows:

1. A bearing assembly comprising:

bearing means having an annular metal inner race portion defining a borefor receiving a journal member therethrough;

a journal member carrying the bearing means in a seat thereon, the seatbeing defined by shoulder means on the journal member, the effectiveoutside diameter of the shoulder means being larger than the insidediameter of the bearing bore;

whereby, during assembly of the bearing means on the journal member, theinner race portion must be momentarily expanded, without exceeding itselastic properties by forceably passing it over the shoulder means tothe seat without permanent deformation or fracture, the bearing beingthereby mounted and positively retained on the journal member.

2. The assembly according to claim 1 wherein the shoulder means compriseannular spaced shoulders on the journal member and define theseattherebetween.

3. The assembly according to claim 1 wherein the journal member is anengine crankshaft.

4. The assembly according to claim 3 wherein the crankshaft is anoutboard engine crankshaft.

5. A crankshaft-bearing assembly comprising:

bearing means having an inner mounting portion defining a bore forreceiving a crankshaft therethrough,

a crankshaft inserted through the bore and receiving the bearing meansin a seat thereon, the seat being defined by a pair of spaced retainingshoulders on the crankshaft, one of the shoulders having an effectivediameter such that it is necessary to momentarily expand the mountingportion of the bearing means to force the bearing means past theshoulder to the seat during assembly.

6. The assembly according to claim 5 wherein the mounting portion is aone-piece annular member.

7. The assembly according to claim 5 wherein the retaining shoulders areannular.

8. The assembly according to claim 7 wherein the shoulders areintegrally formed on the crankshaft.

9. The assembly according to claim 5 wherein the outside diameter of theshoulder is about 0.1 to 0.8 percent larger, 0.4 percent beingpreferred, than the inside diameter of the bearing means bore.

10. The assembly according to claim 5 wherein the bearing mountingportion is a material having a hardness of at least about R and thecrankshaft is a material having a hardness of from about R 35 to R 60whereby galling and permanent deformation are prevented.

1. A bearing assembly comprising: bearing means having an annular metalinner race portion defining a bore for receiving a journal membertherethrough; a journal member carrying the bearing means in a seatthereon, the seat being defined by shoulder means on the journal member,the effective outside diameter of the shoulder means being larger thanthe inside diameter of the bearing bore; whereby, during assembly of thebearing means on the journal member, the inner race portion must bemomentarily expanded, without exceeding its elastic properties byforceably passing it over the shoulder means to the seat withoutpermanent deformation or fracture, the bearing being thereby mounted andpositively retained on the journal member.
 2. The assembly according toclaim 1 wherein the shoulder means comprise annular spaced shoulders onthe journal member and define the seat therebetween.
 3. The assemblyaccording to claim 1 wherein the journal member is an engine crankshaft.4. The assembly according to claim 3 wherein the crankshaft is anoutboard engine crankshaft.
 5. A crankshaft-bearing assembly comprising:bearing means having an inner mounting portion defining a bore forreceiving a crankshaft therethrough, a crankshaft inserted through thebore and receiving the bearing means in a seat thereon, the seat beingdefined by a pair of spaced retaining shoulders on the crankshaft, oneof the shoulders having an effective diameter such that it is necessaryto momentarily expand the mounting portion of the bearing means to forcethe bearing means past the shoulder to the seat during assembly.
 6. Theassembly according to claim 5 wherein the mounting portion is aone-piece annular member.
 7. The assembly according to claim 5 whereinthe retaining shoulders are annular.
 8. The assembly according to claim7 wherein the shoulders are integrally formed on the crankshaft.
 9. Theassembly according to claim 5 wherein the outside diameter of theshoulder is about 0.1 to 0.8 percent larger, 0.4 percent beingpreferred, than the inside diameter of the bearing means bore.
 10. Theassembly according to claim 5 wherein the bearing mounting portion is amaterial having a hardness of at least about Rc 60 and the crankshaft isa material having a hardness of from about Rc 35 to Rc 60 wherebygalling and permanent deformation are prevented.